Terry D. Prowse, Chris Furgal, Barrie R. Bonsal and Thomas W. D. Edwards
Climatic Conditions in Northern Canada:
Past and Future
This article reviews the historical, instrumental, and future
changes in climate for the northern latitudes of Canada.
Discussion of historical climate over the last 10 000 years
focuses on major climatic shifts including the Medieval
Warm Period and the Little Ice Age, and how these
changes compare with those most recently experienced
during the period of instrumental records. In reference to
the latter, details are noted about observed trends in
temperature and precipitation that have been recorded
over the last half century, which exhibit strong west to
east and north to south spatial contrasts. A comprehensive review of future changes is also provided based on
outputs from seven atmosphere–ocean global climate
models and six emission scenarios. Discussion focuses
on annual, seasonal, and related spatial changes for
three 30-year periods centered on the 2020s, 2050s, and
2080s. In summary, substantial changes to temperature
and precipitation are projected for the Canadian North
during the twenty-first century. Although there is considerable variability within the various projections, all scenarios show higher temperature and, for the most part,
increasing precipitation over the entire region.
INTRODUCTION
This paper is one of a series of articles assessing how climate
change has and will continue to affect the ‘‘North’’ of Canada,
specifically the area north of latitude 608N that contains three
large territorial administrative units: Yukon, Northwest Territories, and Nunavut (1). Its major objective is to provide
essential background about changing general climatic conditions, particularly temperature and precipitation, thereby
providing context for changes in other physical, biological,
and human systems that are reviewed in companion articles.
Past climatic conditions are initially addressed by considering
both the instrumental (focused on the last half-century) and preinstrumental (previous 10 millennia) periods. This is followed
by a detailed review of future changes as projected by a suite of
coupled atmosphere–ocean global climate models (AOGCMs)
that were run using a number of future emission scenarios based
on assumed future economic, population growth, technology,
energy, and land use changes. To provide a broad perspective
on future changes, we consider three time intervals centered on
the 2020s, 2050s, and 2080s. Median annual and seasonal values
are reviewed accompanied by a discussion of regional and
intermodel variability.
PAST CLIMATE
Instrumental Period
Several investigations have documented significant climatic
trends over the Canadian North during the instrumental period.
However, the combination of the region’s sparse observations
and high natural variability makes it difficult to distinguish
between signals of climate variability and change with
confidence (2). Serious problems with precipitation measureAmbio Vol. 38, No. 5, July 2009
ment in cold environments (3) increase this uncertainty. Because
few stations in Canada’s North have data prior to 1950,
estimates of trends and variability are limited to approximately
the last half century. From 1950 to 1998, there is a west to east
gradient in mean annual temperature trends, with significant
warming of 1.58C–2.08C in the western Arctic, and a significant
cooling (1.0 to 1.58C) in the extreme northeast (4). Trends
were strongest during winter and spring. In more recent periods,
however, all regions show warming. Annual and winter
temperature anomalies and annual precipitation departures
over four northern regions from 1948 to 2005 (Fig. 1) show
greatest warming in the Yukon and Mackenzie (2.28C and
2.08C, respectively), with smaller warming rates over the Arctic
tundra and Arctic mountain regions (1.38C and 0.88C). In
comparison, temperatures throughout Canada as a whole
increased by 1.28C over this same period (Fig. 1a). Note that
all trends are significant at the 0.05 level. Winter temperatures
in the Yukon and Mackenzie regions have warmed by 4.58C and
4.38C, respectively (Fig. 1b). Many of the extreme warm winters
in these regions have occurred during the latter part of the
record. Winter temperatures over the Arctic tundra region have
increased by 1.78C while the Arctic mountains have experienced
a small (not statistically significant) warming. Springs have also
warmed at a higher rate over the western Arctic; however,
values are slightly lower as compared with winter (not shown).
Summer and autumn are associated with smaller positive trends
over all regions.
The observed temperature increases in Canada’s North were
also reflected in the timing of spring 08C-isotherm dates.
Western Arctic regions showed significant trends toward earlier
dates (5–10 days), whereas central areas were associated with
smaller, generally insignificant earlier trends, and extreme
eastern regions experienced later springs during the last half
century (6). These spatial patterns were also evident in past
variations in the timing of snowmelt and dates of freshwater ice
breakup (7, 8). Snow cover extent has significantly decreased
over most of Canada (including the north), especially during
late winter and early spring (9).
Annual precipitation totals from 1948 to 2005 have increased
throughout all of northern Canada, with the largest increases
over the more northerly Arctic tundra (þ25%) and Arctic
mountain (þ16%) regions (Fig. 1c). The western Arctic is
associated with small, insignificant precipitation increases. The
greater increase in high Arctic regions is evident during all
seasons, with strongest trends in fall, winter, and spring (4). In
terms of extremes, Bonsal et al. (10) found that in northwestern
Canada, the period 1950–1998 experienced a trend toward fewer
days with extreme low temperature and more days with extreme
high temperature during winter, spring, and summer. The
magnitude of heavy precipitation events increased during the
period of record (11), and there has been a marked decadal
increase in heavy snowfall events in northern Canada (12).
The observed trends and variability in temperature and
precipitation over northern Canada are consistent with those
for the entire Arctic (2). Throughout the circumpolar Arctic
(north of 608N), annual air temperatures during the twentieth
century increased by 0.098C per decade. This included a general
increase from 1900 to the mid-1940s, decreases until the mid-
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257
Figure 1. Regional temperature anomalies and precipitation departures from normal in the Canadian North from 1948 to 2005: (a) annual
temperature; (b) winter temperature; (c) annual precipitation. Regions include Yukon/North BC mountains (YK), Mackenzie District (MD),
Arctic tundra (AT), Arctic mountains and fiords (AM), and all of Canada (CA) (see corresponding map of climate regions [d]). Units are 8C for
temperature and percentage departures from normal for precipitation, both relative to the 1951–1980 reference period. Linear trends over the
period of record are given in parentheses. Asterisks signify significant trends at the 0.05 level. Data were obtained from Environment
Canada’s Climate Trends and Variations Bulletin (5).
1960s, and accelerated increases thereafter. Although most
pronounced in winter and spring, all seasons exhibited an
increase in temperature over the past several decades. In terms
of precipitation, the entire Arctic has shown a significant
positive trend of 1.4% per decade for the period 1900 to 2003.
Largest increases generally occurred in fall and winter. Some
investigations also suggested that the fraction of annual
precipitation falling as snow has diminished, which is consistent
with widespread temperature increases (2).
Pre-instrumental Period
The pre-instrumental climate history of northern Canada is
known from various natural archives including tree rings, lake
and marine sediments, and glacier ice, and from the mapping
and dating of glacial moraines and other geomorphic features
(2). The climate of the North during the last 10 000 years has
been characterized by relative warmth and remarkable stability
in comparison to the cold and variable conditions of the
previous glacial interval (Fig. 2). In the last 2000 years, climate
has been characterized by multicentennial oscillations ranging
from mild conditions (similar to the modern era) during the
so-called Medieval Warm Period, to widespread persistence of
relatively cool conditions during the Little Ice Age (LIA)
(Fig. 3). The general pattern of variability is believed to
primarily reflect long-term natural fluctuations in circumpolar
atmospheric circulation, expressed during the LIA for example,
258
by increased southward penetration of cold Arctic air due to
intensified meridional circulation (15).
Climate of the last 400 years has been characterized by
progressive warming and related changes over most of the
Arctic, including retreat of glaciers, reduction in sea-ice extent,
permafrost melting, and alteration of terrestrial and aquatic
ecosystems (16). During the past approximately 150 years,
however, it is evident that the rate and nature of change are
unprecedented since the abrupt warming at the onset of the
current interglacial period over 10 000 years ago (Fig. 3). This
rapid acceleration in temperature increase over the Arctic is
projected to continue throughout the twenty-first century (17).
Figure 2. Temperature change (departure from present) during the
past 100 000 years reconstructed from oxygen-isotope data from a
Greenland ice core (13).
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FUTURE CLIMATE
Background
Figure 3. Reconstruction of Northern Hemisphere mean annual
temperature, expressed as departures from the twentieth century
mean (data from Moberg et al. [14]).
To assess climate-change impacts on societies, ecosystems, and
infrastructure, we must first project likely changes in the
physical climate. The tools most commonly adopted for
projecting future climate are AOGCMs. These models describe
the main dynamic and physical processes, interactions, and
feedbacks of the climate system, and are used to generate
climatic responses to given changes in greenhouse gas (GHG)
and aerosol concentrations. The ability of these models to
simulate climate is best at large scales. At smaller spatial scales,
AOGCMs still provide useful information on climate change;
however, they do not capture many features in local climate
such as heavy precipitation events (17, 18).
There are two key uncertainties concerning future climate
projections. These include unknown GHG and aerosol emissions, and differences in the regional pattern of climate change
simulated by individual models. Regarding the former, a special
report on emissions scenarios (SRES) quantified several future
emission scenarios based on assumptions of future economic
and population growth, technology, and energy and land use
changes (19). In all, 40 scenarios were developed (based on four
Figure 4. Scatter plots of projected
mean annual temperature and precipitation changes in western (left)
and eastern (right) regions of
northern Canada for the 30-year
periods centered on the 2020s,
2050s, and 2080s. Boundary between the west and east is at
1028W. Gray squares indicate natural climate variability as simulated by the Canadian CGCM2 model.
Ambio Vol. 38, No. 5, July 2009
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259
Figure 5. Scatter plots of projected
seasonal temperature and precipitation changes over western (left)
and eastern (right) regions of
northern Canada for the 30-year
period centered on the 2050s.
Boundary between the west and
east is at 1028W. Gray squares
indicate natural climate variability
as simulated by the Canadian
CGCM2 model.
storylines labeled A1, A2, B1, and B2), six of which were used as
‘‘marker’’ scenarios by the Intergovernmental Panel on Climate
Change (IPCC). Three technological futures were used as
illustrations for the A1 storyline, including A1FI (fossil
intensive), A1T (predominantly nonfossil), and A1B (balanced).
One illustrative scenario represents each of the A2, B1, and B2
storylines. In descending order of radiative forcing by 2100,
these scenarios rank as A1FI, A2, A1B, B2, A1T, B1. The
second uncertainty arises from the various representations of
physical processes and feedbacks by individual AOGCMs. As a
result, each model simulates a different global mean and
regional pattern of change in variables such as temperature and
precipitation. This is of particular concern in the Arctic where
climate is influenced by numerous complex interactions and
feedbacks at a variety of spatial and temporal scales. For
example, sea ice and the Arctic Ocean are not well represented
in current AOGCMs, which can have large implications to
projected temperature changes due to feedbacks associated with
an ice-covered surface (17).
Given the variety of models and emission scenarios, the
selection of AOGCM simulations for impact assessment is not
260
straightforward. McAvaney et al. (20) concluded that at this time,
no single model can be considered best, and it is therefore
important to utilize results from a range of simulations. Another
important criterion for AOGCM selection involves its validity, as
evaluated by simulation of present-day and past climates.
Detailed model comparisons for the Arctic determined spatial
differences in terms of simulated temperature, while precipitation
was substantially overestimated by all models (21). The Arctic
Climate Impact Assessment assessed the ability of five AOGCMs
to simulate 1981–2000 baseline climate over four Arctic regions
and concluded that annual mean temperature was, on average,
reasonably well replicated; however, there was considerable
intermodel and seasonal variability on a regional basis (17). As
with other assessments, there were major systematic overpredictions in precipitation, particularly during winter and spring.
Comparisons of seven AOGCMs to simulate the mean values and
spatial variability of current temperature and precipitation over
four regions spanning northern Canada revealed considerable
interregional and seasonal variability, again with temperature
being more accurately simulated than precipitation (22). The
British Hadley Centre for Climate Prediction and Research, the
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Ambio Vol. 38, No. 5, July 2009
Figure 6. Maps of projected mean annual temperature changes over the Canadian North for the 30-year periods centered on the 2020s, 2050s,
and 2080s.
German Max Planck Institut für Meteorologie, and the Japanese
Centre for Climate Research Studies (CCSRNIES) models best
replicated annual and seasonal temperature over all subregions,
with the Canadian Centre for Climate Modelling and Analysis
(CGCM2) and American National Centre for Atmospheric
Research (NCAR-PCM) models having intermediate accuracy,
and the Australian Commonwealth Scientific and Industrial
Research Organisation and American Geophysical Fluid Dynamics Laboratory models being least representative. Collectively, the AOGCM temperature simulations displayed a similar
degree of accuracy over all subregions. Conversely, precipitation
was only accurately simulated by the majority of models over
northern Quebec and Labrador. Annual and seasonal precipitation amounts were substantially overestimated by all AOGCMs
in the western and central Canadian Arctic.
Climate-Change Projections for the Canadian North
Climate-change scenarios for the Canadian North are derived
from the seven AOGCMs recommended by the IPCC using the
Ambio Vol. 38, No. 5, July 2009
six SRES emissions scenarios described previously. The
scenarios provide climate changes with respect to 1961–1990
baseline for the 30-year periods centered on the 2020s (2010–
2039), 2050s (2040–2069), and 2080s (2070–2099) in scatter plot
and map format. Scatter plots summarize mean temperature
and precipitation changes averaged over a particular region (see
Figs. 4 and 5). Each color represents a specific AOGCM while
the symbols signify the different emission scenarios. The gray
squares depict ‘‘natural’’ climate variability as simulated by the
Canadian CGCM2. These have been derived from a long
(;1000 year) control run with no change in GHG and aerosol
forcing. If the colored symbols and the gray boxes overlap, then
these scenarios lie within the range of projected natural climate
variability. The blue lines represent median temperature and
precipitation changes and aid in the identification of cooler,
warmer, drier, or wetter scenarios. For the climate-change maps
(Figs. 6 to 9), all scenarios have been interpolated onto the
CGCM2 grid and then the minimum, median, and maximum
changes are calculated and plotted. As a result, the values for
each grid are not necessarily from the same scenario.
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Figure 7. Maps of projected seasonal temperature changes over the Canadian North for the 30-year period centered on the 2050s.
Scatter plots for western and eastern areas of the North,
divided at 1028W longitude, reveal little difference in projections
between the two regions (Fig. 4). As expected, intermodel
variability increases dramatically farther into the future. For the
2020s, both the west and east exhibit mean annual temperature
changes concentrated near þ28C and precipitation increases
near 5%–8%. Temperatures range from approximately þ18C to
þ38C and precipitation from near 0%–12%. The 2050s show
higher increases in both temperature and precipitation. Temperature projections vary from þ28C to þ78C with a median
value of slightly under þ48C. Precipitation increases are 5%–25%
with a median of 15%. Intermodel variability is greatest during
the 2080s. Over the west, median temperature changes are near
þ68C but range from þ3.58C (NCAR-PCM B2 scenario) to
þ12.58C (CCSRNIES A1F1 scenario). The majority of values
are between þ58C and þ78C (Fig. 4). For precipitation, increases
range from 8% (CGCM2 B2) to 40% (CCSRNIES A1F1) with a
median value of just over 20%. Most scenarios project a 15%–
30% increase in annual precipitation. Note that projections
during all periods fall outside the range of modeled natural
variability as indicated by the gray squares in Figure 4.
Projected seasonal climate changes are given in the scatter
plots for the 2050s (Fig. 5). The seasons correspond to winter
(December-January-February), spring (March-April-May),
summer (June-July-August), and fall (September-October-November). The climate projections reveal considerable intermodel
variability, particularly during winter (and to a lesser extent,
spring and fall). Highest temperature changes occur during
winter. The eastern Canadian Arctic is associated with slightly
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higher projections of winter temperature (median þ5.58C; range
þ48C to þ98C) than the west (median þ4.58C; range þ2.58C to
þ10.58C). Median spring changes are similar for the west and
east (near þ38C); however, there is slightly more intermodel
variability in the west. Projected fall temperatures are greater
than spring (; þ48C to þ4.58C) with the CCSRNIES model
consistently showing greatest changes over both the west and
the east. Summer has the lowest temperature projections and
the least amount of intermodel scatter. Median changes are near
þ28C and range from þ18C to þ38C. With respect to
precipitation changes, values during winter range from near
0% over both regions to over 40% in the east, with most
scenarios projecting winter precipitation increases of 20%–30%.
Spring shows more consistent results among the models with
lower projected increases than winter. Values range from near
0%–30% with a median of 15%. Fall is similar to spring
although slightly higher median increases are projected over the
western Arctic as compared with the east. During summer, all
models project increases between 5% and 20% with median
values at 10%. As with temperature, summer has the lowest
intermodel variability for precipitation.
Figure 5 also illustrates individual model clusters associated
with several of the seasonal projections. In particular, the
Canadian CGCM2 model (black symbols) consistently projects
the lowest precipitation changes during winter, spring, and fall
for both the western and eastern Canadian Arctic. In fact, in
winter, some scenarios even project a decrease in precipitation.
Another notable deviation involves the CCRSNIES AOGCM
(green symbols) that, for the most part, projects much higher
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Ambio Vol. 38, No. 5, July 2009
Figure 8. Maps of projected annual precipitation changes over the Canadian North for the 30-year periods centered on the 2020s, 2050s, and
2080s.
temperature increases as compared with the other scenarios.
These differences likely reflect varying individual model physics
and parameterizations of surface boundary conditions such as
sea ice.
Spatial characteristics of annual and seasonal projected
temperature changes over northern Canada indicate greatest
temperature changes at higher latitudes, particularly in the
extreme northwest (Figs. 6 and 7). Seasonally, greatest
temperature changes over the entire region are projected to
occur during winter and fall. The majority of projections exhibit
a strong poleward gradient in temperature changes. This is
particularly evident for the 2050s and 2080s and is more
pronounced in winter and to a lesser extent fall and spring. For
example, over western land regions, there is a 28C–48C
difference in warming between southern and northern areas
for the 2050s median projection during winter and fall,
increasing to 48C–68C in the maximum projection. The gradient
in changes equates to a more uniform future temperature
climate over northern land areas, which could have severe
hydrologic implications for northward flowing rivers (e.g., ice
jamming) (23).
Annual and seasonal precipitation changes show considerable spatial variability over the Canadian Arctic, with the
greatest annual percentage increases projected over more
northerly regions (Figs. 8 and 9). Seasonal maps for the 2050s
display even higher variability with minimum changes even
associated with decreases in precipitation over parts of the
region during all seasons. The median projections tend to show
greatest increases during winter and fall, particularly over more
northerly regions. The maximum scenario indicates the highest
future precipitation changes over the eastern Arctic.
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In summary, substantial changes to temperature and
precipitation are projected for the Canadian North during this
century. Although there is considerable variability within the
various projections, all scenarios show higher temperature and
for the most part, increasing precipitation over the entire region.
These increases are projected to occur during all seasons with
greatest changes during winter and to a lesser extent spring and
fall. Spatially, greatest temperature increases are shown at
higher latitudes (particularly over the Arctic Ocean) with
decreasing changes in a southerly direction. Projected precipitation changes are more spatially variable although increases
tend to be most prominent at higher latitudes.
The high degree of variability inherent in Arctic climate
increases the uncertainties of projected future temperature and
precipitation. Given the findings of Bonsal and Prowse (22), it is
recommended that a range of future climate projections be used
when examining potential impacts across the North. Individual
model outliers such as the CGCM2 low precipitation projections and the CCRSNIES high temperature–precipitation
increases (Figs. 4 and 5) should be used with caution because
of their discrepancies with other model projections.
SUMMARY
In general, the climate of the North over the last 10 000 years
has been characterized by relative warmth and remarkable
stability in comparison to the cold and variable conditions of
the previous glacial interval. Within the last 2000 years, the
climate has been characterized by multicentennial oscillations
ranging from mild conditions (similar to the modern era) during
the so-called Medieval Warm Period to widespread persistence
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263
Figure 9. Maps of projected seasonal precipitation changes over the Canadian North for the 30-year period centered on the 2050s.
of relatively cool conditions during the Little Ice Age.
Progressive warming over the last 400 years has led to a
number of changes in the cryosphere including, for example, the
retreat of glaciers, reductions in sea-ice extent, and permafrost
thawing. During the past approximately 150 years, however, it
is evident that the rate and nature of change are unprecedented
since the abrupt warming at the onset of the current interglacial
period over 10 000 years ago.
Although the instrumental network is sparse and presents
difficulties in making interpretations, the overall observed
warming and increased precipitation over northern Canada is
consistent with that for the entire Arctic. The Canadian North,
however, has also been associated with distinctive east–west and
north–south spatial contrasts. The period 1950–1998 was
characterized by a west to east gradient in mean annual
temperature trends, with significant warming (cooling) in the
western (northeastern) Arctic. Trends were strongest during
winter and spring. In more recent periods, however, all areas
exhibit warming, which is most pronounced in the Yukon and
Mackenzie and less so in the Arctic tundra and Arctic mountain
regions. Similar trends are observed in the timing of spring melt
conditions. Specifically, the western (eastern) Arctic experienced
earlier (later) springs during the last half century, as evidenced
by the timing of the 08C-isotherm, the breakup of freshwater
ice, and snowmelt. Over approximately the last half century,
annual precipitation has increased across northern Canada, the
largest increases being in the most northerly latitudes of the
Arctic tundra (þ25%) and Arctic mountains (þ16%), while only
small, insignificant increases occurred in the western Arctic.
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Over most of Canada, including the northern latitudes, the
combination of temperature and precipitation has resulted in a
significant decrease in the spatial extent of snow cover,
especially during late winter and early spring.
The projected precipitation and temperature scenarios for
the Canadian North derived from the seven AOGCMs and six
SRES emissions scenarios showed increasing intermodel variability with time. For the 30-year period centered on the 2020s,
overall model projections indicate an approximate þ28C
warming in the western and eastern portions of the Canadian
Arctic along with ;7% increase in precipitation. These values
almost double (triple) for the 2050s (2080s) at ;þ48C (;þ68C)
and ;þ15% (;þ21%) for air temperature and precipitation,
with only minor variations in median values between western
and eastern Arctic regions. In general, the greatest temperature
changes are projected to occur in the fall and winter months for
both regions. A closer examination of the projected spatial
characteristics of annual and seasonal temperatures revealed a
general poleward gradient of temperature increase, which will
likely lead to a more uniform, future temperature climate over
northern land areas.
Future precipitation projections vary most among models,
although median values indicate greatest increases in winter
(just under 20% for both regions), and summer increases of
about 10% in the west and 14% in the east. Spring and autumn
values fall in between these seasonal extremes. Although there is
significant spatial variability in annual and seasonal precipitation changes, the largest annual percentage increases are
projected for the more northerly regions of the Canadian Arctic.
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Terry D. Prowse is a Professor, Research Chair and Senior
Scientist specializing in climate-change effects on cold regions
hydrology and aquatic ecosystems. His address: Water and
Climate Impacts Research Centre, Environment Canada,
Department of Geography, University of Victoria, PO Box
3060 STN CSC, Victoria, BC, V8W 3R4, Canada.
E-mail: terry.prowse@ec.gc.caa
Chris Furgal is an Assistant Professor in the Indigenous
Environmental Studies Program at Trent University, Peterborough, Ontario. He has a background in the biological and
social sciences and conducts work on Indigenous environmental health issues, with a particular emphasis on circumpolar regions. His address: Indigenous Environmental Studies
Program, Trent University, 1600 West Bank Drive, Peterborough, ON, K9J 7B8, Canada.
E-mail: chrisfurgal@trentu.ca
Barrie R. Bonsal is a Research Scientist with Environment
Canada in Saskatoon, Saskatchewan. Specialization involves
assessing past and projected future climatological impacts on
the hydrology and ecology of Canada and the Northern
Hemisphere. His address: National Water Research Institute,
National Hydrology Research Centre, Environment Canada,
11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada.
E-mail: barrie.bonsal@ec.gc.ca
Thomas W. D. Edwards is a professor in the Department of
Earth and Environmental Sciences at the University of
Waterloo, Canada, specializing in isotope hydrology and
hydroclimatology. His current research is focused on the
effects of past and ongoing climate change on water resources
in Canada and Fennoscandia. His address: Department of
Earth and Environmental Sciences, University of Waterloo,
200 University Avenue West, Waterloo, ON, N2L 3G1,
Canada.
E-mail: twdedwar@uwaterloo.ca
Ó Royal Swedish Academy of Sciences 2009
http://www.ambio.kva.se
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